1. Field of the Invention
The present invention relates to an IC suction mechanism and method, for sucking up an IC accommodated on a tray, and a horizontal conveyer type automatic handler incorporating the IC suction mechanism.
2. Description of Related Art
Explanation will be made of an IC suction mechanism according to an earlier development, with reference to FIGS. 7 to 12.
At first, the arrangement of a horizontal conveyer type automatic handler incorporating a suction mechanism (that is, a suction unit 2 in this example) for ICs.
Referring to FIG. 7 which is a plan view illustrating the arrangement of the horizontal conveyer type automatic handler, there are shown a supply part 1A, a preheat part 1B, a measuring part 1C, an accommodation part 1D, a supply hand 1E, an accommodation hand 1F, a loader 1G and an unloader 1H.
The horizontal conveyer type automatic handler 1 conveys an IC by horizontally shifting an IC carrier (which is not shown).
The supply hand 1E incorporates a plurality of supply suction units 2 (IC suction mechanisms) which will be explained later. The loader 1G carries a tray thereon in which a plurality of ICs 5 to be tested are accommodated. The unloader 1H carries thereon an empty tray.
Referring to FIG. 8, which is a perspective view illustrating a tray used in the loader 1G and the unloader 1H, a plurality of recesses 4a, e.g., in the example shown in FIG. 8, comprising a matrix of 4 lines and 5 rows, for accommodating the ICs 5 to be tested, are formed longitudinally and transversely on the tray 4.
Referring to FIG. 9 which is a perspective view illustrating an IC to be tested, an flat package IC 5 having a surface mounting shape is the object to be sorted by the horizontal conveyer type automatic handler.
Next, explanation will be made of the operation of the horizontal conveyer type automatic handler shown in FIG. 7.
The trays 4 which carry thereon the ICs 5 which have not yet been tested, are shifted onto the loader 1G by an operator. The supply hand 1E successively shifts the ICs from the topmost one of the trays 4 on the loader 1G onto the IC carrier located in the supply part 1A.
The IC carrier in which the ICs 5 are accommodated by a predetermined number is shifted from the supply part 1A to the preheat part 1B. When the ICs 5 are heated up to a predetermined temperature in the preheat part 1B, the IC carrier is shifted into the measuring part 1C.
After the ICs 5 are tested in the measuring part 1C, the IC carrier is shifted into the accommodation part 1D. The ICs 5 are sorted and shifted into a tray 4 on the unloader 1H by means of the accommodation hand 1F. The IC carrier which is emptied in the accommodation part 1F is returned to the supply part 1A.
Thus, the IC carrier is circulated in the automatic handler 1 through the supply part 1A, the preheat part 1B, the measuring part 1C, the accommodation part 1D and the supply part 1A in the mentioned order.
Next, an explanation will be made of an earlier developed IC suction mechanism (suction unit) with reference to FIGS. 10A and 10B.
Referring to FIGS. 10A and 10B which shows a suction unit as an example of the conventional IC suction mechanism, and in which FIG. 10A is a front view and FIG. 10B is a vertical sectional view, there are shown a suction unit 2, a suction pad 2A, a shaft 2B, a compression coil spring 2C, a direct acting bearing 2D, a holder 2E and a guide 2F.
In FIGS. 10A and 10B, the hollow conical shape suction pad 2A formed of elastic material such as rubber, is attached to the lower end part of the hollow shaft 2B. The cylindrical guide 2F is attached to the shaft 2B so as to cover the suction pad 2A. It is noted that with the provision of the guide 2F, there has been proved that the capability of suction can be enhanced.
The shank part of the shaft 2B is slidably held by the direct acting bearing 2D enclosed in the holder 2E. The compression spring 2C wound on the shank part of the shaft 2B is located between the guide 2F and the holder 2E so as to apply a force for separating the guide 2F and the holder 2E from each other. The shaft 2B is formed at its upper end part with a flange for limiting the motion of the shaft 2B.
The shaft 2B is attached thereon with a tube communicated with the hollow part thereof and having a distal end connected with a vacuum pump (suction means). That is, when the vacuum pump sucks up the air in such a condition that the suction pad 2A is made into contact with the IC 5, the IC5 is sucked up by the suction pad 2A.
Referring to FIGS. 10A and 10B, the suction unit 2 has such a structure that when the holder 2E is lowered so as to allow the suction pad 2A to make contact with the IC, and the suction pad 2A incorporating the suction unit 2A slides so as to absorb unevenness of thickness of packages of the ICs without application of excessive stress to the ICs 5.
Referring to FIG. 11 which shows such a condition that the ICs 5 accommodated on the tray 4 are sucked, the IC pad 2A is made into contact with the IC 5 and a gap C is defined between the upper surface of the holder 2E and the flange of the shaft 2B. In this condition, the IC 5 is sucked up as mentioned above.
FIG. 12 shows such a condition that no IC are accommodated on the tray 4. In FIG. 12, the holder 2E descends to the same position as that of FIG. 11. In this figure, because there are no IC 5 on the tray 4, the IC pad 2A is brought into contact with the bottom surface of the tray 4.
In the above-mentioned condition shown in FIG. 12, the horizontal conveyer type automatic handler 1 determines that the IC is sucked up, and accordingly, it tries to convey the tray 4 into the supply part 1A in this condition. However, the tray 4 is extremely heavy in comparison with the IC 5, the supply hand 1E cannot convey the tray 4 so that the suction is released. In this case, the horizontal conveyer type handler 1 determines that it drops the IC 5 so as to stop the operation at that time, indicating dropping of the IC 5.
The above-mentioned indication does mean that the suck-up of the IC is inferior. That is, it is erroneously recognized and determined that the supply hand 1E drops the IC5 during shifting.